Printing blanket



April 30, 1935. H 1 LUEHRS 1,999,733

PRINTING BLANKET Filed Aug. 16, 1953 F/G. I

HAA/.S J. L UEHRJNVENTOR.

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Patented Apr. 30, 1935 UNITED STATES PAT-ENT OFFICE i v v 1 ,999,733

rmNTNG BLANKET Hans J; Luehrs, `Wsterly, RgI; Application August 16,933","s ria1 No. '685325 6 Claims.

The objects of my invention are to provide a printing blanket with adesirable hard impression surface having improved ink-repellentqualities and a more permanent resistance against deformation combinedwith the necessary resiliency in order to enable the blanket surface toconform tothe typehigh variation of the printing plate and whereby toavoid the embedding of the types into the impression surface, preventingthe rounding off of the type edges and affcrd an easier slippage of thepaper web, thereby reducing 'the known paper breaks.

The features of my invention are more fully set forth in theaccompanying drawing, forming a part of this specification, in which:

Fig. 1 is a cross-sectional View of a printing blanket embodying myinvention comprising an outer impression member and an inner orsupporting resilient member.

Fig. 2 is a similar View showing a modification.

Fig. 3 shows a still further modification including a resilient memberof non-uniform compressibility.

Fig. 4 is a modification of the blanket shown in Fig. 3.

In Fig. 1 the printing blanket consists of a layer of soft rubber orother resilient material 3 as a base, and a printing surface 2 in theform of a thin fiexible steel sheet or' other hard but fiexible materialof a high elastic moduus. The blanket is attached to the-impressioncylinder in the usual manner either in individual layers or as anintegral manufactured unit. Fig. 2 represents a printing blanketconsisting of a base layer of soft rubber or other resilient material 3,a thin flexible steel sheet or metal screen of a high elastic modulus orother hard but fiexible material 4 as a reinforcement to' providesufricient hardness and a thin outer layer of rubber, paper or othersuitable material 5 as a printing surface. Fig. 3 shows a blanketcomprising a base layer 6 of rubber or like material of nonuniformcompressibility in which the meeting edge portions 1, 'I are of greatercompressibility graduating towards the middle 'of the blanket then thecentral portion 8 thereof.

Fig. 4 shows a blanket in which the base resilient member 9 has itslower or cylinder contacting surface shaped in the form of a suitableparabolic curve.

One of the features or objeots of my invention is to provide a printingblanket adapted to be mounted on the cylinder in initially preloadedcondition which may be defined as a condition under which a definitelypredetermined load or compression is put upon the resilient base of theblanket whereby shifting and non-uniformity is avoided. If the baselayer of the blanket is of the same size as the outer con- 5 tact layeror is merely compressed when the blanket is put on the cylinder withoutdefinite provision having been made against casual or unevencompression, a true circular printing surface cannot be obtained, or isat least very diffi- 10 cult to attain. The object of mounting theprinting blanket in predetermined initialiy preloaded condition may beaccomplished by making the resilient member in Figures 1 and 2 oversize.Or as disclosed in Figure 3 the re- 15 -si1ient member may be ofnon-uniform compressibility circumferentially or as shown in Figure 4the lower surface of the resilient member may be shaped in the form of aparabolic curve.

When a blanket is clamped down on the cy1- inder, the greatestcompression occurs of course at the meeting edges of the blanket. Hencean uneven compression or load is created and the desired truecylindrical form of the printing surface cannot be had. If however, theresilient layer is prepared so as to have greater compressibility,inherent in the composition as in Figure 3 or by reason of the form asin Figure 4, an even load all around is obtained and the printingsurface member may be mounted in the 30 form of a true circle. Thisobject may be accomplished by making the resilient member oversize inall the forms shown, in order to obtain a compressed condition of thesupporting member while the blanket is clamped down to the properprinting pitch diameter. Another object of my invention is to provide ablanket of such form that when mounted, the preloaded printing surfaceremains parallel to the surface of the impression cylinder.

It will be obvious that my blanket provides effective ink repellence toavoid oifsets, conforms easier to plate or cylinder Variation andprovides a better possibility of maintaining a correct printing pitch.My blanket also eliminates the em- 45 bedding of the types on account ofthe hard but resilient impression surface and therefore avoids theundesirable wear of the type edges which is a well' known disadvantagewith softer blankets. The elimination of the embedding of the types isalso desirable as it permits easy slippage of the paper web andtherefore will diminish paper breaks.

Although I have illustrated and described my invention' in its preferredform, modifications may latter having its lower surface shaped to form aparabolic curve.

3. A printing blanket comprisng an impres'sion member and a, resilientinner supporting member therefore, the latter having its lower surfaceshaped in the form of a parabolic curve;

4. A printing blanket comprising an outer impression member and a.compressible inner supporting member therefore, the latter havinggreater compressibility at its meeting edges than at its centralportion.

5. A printing blanket comprising a resilient compressible supportingmember having greater compressibility at its'meeting edges than at itscentral portion, a. thin outer impression member and a. reinforcingmetal member interposed between the said. two other members.

i 6. A printing blanket comprising an outer impression member and aninner resilient com'- pressible supporting member having a predeterminedgreater degree of compressibility at the meeting edges of said blanketthan at the inside area thereof whereby to mount said blanket in apredetermined initially loaded condition.

HANS J. LUEHRS.

